Spinal stenosis is a spinal condition that causes a narrowing in one or more areas of the spine. The narrowing can occur at the center of the spine, in the canals branching off the spine, and/or between the vertebrae of the spine. The narrowing can put pressure on the spinal cord and/or on the nerves that branch out from the compressed areas. Similarly, the narrowing can also put pressure on, and restrict the flow of blood in blood vessels in these areas. Spinal stenosis can lead to a number of symptoms including cramping, pain, and numbness in the legs, back, neck, shoulders and arms; a loss of sensation in extremities; and even problems with bladder or bowel function.
Implantable devices that create additional space for the spinal cord, spinal nerves, and/or blood vessels may be used to treat spinal stenosis. Some devices create the necessary space by distracting the spinous processes of adjacent vertebrae. However, the spinous processes are relatively fragile and may be easily damaged, fractured, or even broken off, by devices exerting force on these vertebral components. In some cases, the softer spinous process yields to the device, leading to a recurrence of the stenosis. In other cases, the device may be reincorporated into the softer spinous process, effectively providing no benefit in reducing the symptoms of spinal stenosis.